The present invention relates to a repair fuse device.
Semiconductor memory device includes numerous fine memory cells and logic circuits to drive the fine memory cells. Hence, the fabrication of semiconductor memory devices requires a large number of processes. Defects inevitably occur while such processes are performed. If a defect occurs in any one of the memory cells, the corresponding semiconductor memory device cannot operate normally. However, it is inefficient to discard the entire semiconductor memory device for defects in only several of its memory cells.
Therefore, a repair method is employed for most semiconductor memory devices, in which redundancy cells are formed within a memory to replace defective cells when defects occur in some of the main memory cells.
In such a method using redundancy cells, the replacement of defective cells is performed by cutting fuses corresponding to addresses of the defective cells and cutting enable fuses indicating the use of corresponding repair fuse sets. That is, the defective cells are repaired not when the fuses corresponding to the addresses of the defective cells are cut, but when the enable fuses are cut. Thus, the cutting of the enable fuses is performed for each repair.
As such, the cutting of the enable fuses must be performed as many times as the number of required repairs. As a result, when one wafer is repaired, the cutting of the enable fuses is performed several tens of thousands to several hundreds of thousands of times. Also, as the more repairing process is required, the more probability of repair failure exist. Therefore, increased number of fuse cutting job lowers production yield.